Polymer Chemistry Chapter 10 Quiz

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Questions and Answers

What are the two general classes of polymers?

Amorphous and crystalline

Thermoplastics and thermosets (correct)

Linear and branched

Addition and condensation

What happens to the melting point as molecular weight increases?

increases

As the degree of branching increases, what happens to density?

decreases

What is a plastic that has two monomers in its molecular structure called?

dimer Signup and view all the answers

A polymer in which the chains are highly ordered is said to be:

crystalline Signup and view all the answers

What is the term for a polymer with essentially random chain arrangement?

amorphous Signup and view all the answers

The stiffer HDPE is associated with what kind of molecular weight?

higher Signup and view all the answers

What is the molecular structural difference between HDPE, LDPE, and LLDPE?

HDPE has linear chains, LDPE has highly branched chains, and LLDPE has short, branched chains. Signup and view all the answers

What is the process of improving properties of plastic film by stretching in one or two directions called?

Orientation Signup and view all the answers

LLDPE stands for?

linear low-density polyethylene Signup and view all the answers

PP stands for?

polypropylene Signup and view all the answers

PS stands for?

polystyrene Signup and view all the answers

PVC stands for?

polyvinyl chloride Signup and view all the answers

EVOH stands for?

ethylene-vinyl alcohol Signup and view all the answers

PA stands for?

polyamide Signup and view all the answers

PET stands for?

polyethylene terephthalate Signup and view all the answers

PVDC stands for?

polyvinylidene chloride Signup and view all the answers

OPP stands for?

oriented polypropylene Signup and view all the answers

PVAC stands for?

polyvinyl acetate Signup and view all the answers

What is a distinguishing feature of a polymer with lower crystallinity compared to one with higher crystallinity?

better clarity Signup and view all the answers

How do the general properties of thermoplastics and thermosets differ?

Thermosets have higher potential use temperatures and resistance to solvents. Signup and view all the answers

What properties of plastics are affected by the molecule's degree of polarity?

melting point, solubility, barrier properties, coefficient of friction Signup and view all the answers

How are heat-shrink properties imparted to a polymer?

Using a combination of thermal and mechanical history to produce shrink film. Signup and view all the answers

What is cold flow?

Deformation of plastics under load, also referred to as 'creep'. Signup and view all the answers

Why are all plastics clear in the melt state?

Due to rapid molecular movement that prevents ordering of molecules. Signup and view all the answers

Which two common packaging plastics are predominantly nonpolar?

polyethylene and polypropylene Signup and view all the answers

From what raw material source are most packaging plastics made?

petrochemicals Signup and view all the answers

What is the purpose of flame or corona treatment?

To impart polarity to the surface of low-polarity plastics. Signup and view all the answers

Which has the higher melting point: high-molecular-weight polysulfone or low-molecular-weight polysulfone?

High-molecular-weight polysulfone Signup and view all the answers

What is the purpose and advantage of producing copolymers?

To bring together favorable properties of distinctly different polymers. Signup and view all the answers

Study Notes

Polymer Classes

Two main types of polymers: thermoplastics and thermosets.
Thermoplastics are widely used in packaging; they can reshape upon heating.
Thermosets have cross-linked structures and remain fixed once set, unable to be reshaped.

Molecular Weight and Properties

As molecular weight increases, melting point also increases.
Higher molecular weight in HDPE results in increased stiffness.

Structural Characteristics

Increased branching in polymer molecular structure leads to decreased density.
HDPE features linear chains, while LDPE has highly branched chains, and LLDPE possesses short, branched chains.

Polymer Conformation

Polymers can be crystalline with ordered chains, or amorphous with random arrangements.
Crystalline polymers tend to have higher density and lower clarity compared to amorphous types.

Orientation and Stretching

Orientation of polymer molecules through stretching enhances properties by aligning them along the stress direction.

Common Polymers and Their Acronyms

LLDPE: Linear low-density polyethylene
PP: Polypropylene
PS: Polystyrene
PVC: Polyvinyl chloride
EVOH: Ethylene-vinyl alcohol
PA: Polyamide
PET: Polyethylene terephthalate
PVDC: Polyvinylidene chloride
OPP: Oriented polypropylene
PVAC: Polyvinyl acetate

Physical Properties and Applications

Clarity is generally lower in more crystalline polymers compared to amorphous ones.
Thermosets are designed for higher use temperatures and solvent resistance.

Influence of Polarity

Polarity affects melting point, solubility, barrier properties, and coefficient of friction in plastics.

Heat and Cold Flow

Heat-shrink properties are developed through specific thermal and mechanical processing.
Cold flow, or "creep," is crucial in applications where plastics bear significant loads.

Behavior in Melt State

All plastics appear clear in their melt state due to the rapid motion of molecules, preventing any structured arrangement.

Material Sources

The majority of packaging plastics originate from petrochemical sources.
Common packaging plastics like polyethylene and polypropylene are predominantly nonpolar.

Surface Treatment

Flame or corona treatment enhances surface polarity, improving adhesion properties for low-polarity plastics.

Melting Points of Polymers

High molecular weight polysulfone exhibits a higher melting point compared to lower molecular weight counterparts.

Copolymers

Copolymers combine the beneficial properties of different polymers, allowing for improved material performance.

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Description

Test your understanding of polymer chemistry as presented in Chapter 10. This quiz focuses on the two main classes of polymers, their applications in packaging, and their molecular structures. Perfect for nonchemists looking to deepen their knowledge in this area.